Methods for etching metal interconnect layers

Abstract

In some examples, a method comprises: obtaining a substrate having at a metal interconnect layer deposited over the substrate; forming a first dielectric layer on the metal interconnect layer; forming a second dielectric layer on the first dielectric layer; forming a capacitor metal layer on the second dielectric layer; patterning and etching the capacitor metal layer and the second dielectric layer to the first dielectric layer to leave a portion of the capacitor metal layer and the second dielectric layer on the first dielectric layer; forming an anti-reflective coating to cover the portion of the capacitor metal layer and the second dielectric layer, and to cover the metal interconnect layer; and patterning the metal interconnect layer to form a first metal layer and a second metal layer.

What is claimed is: 
     
       1. A method comprising:
 obtaining a substrate having at a metal interconnect layer deposited above the substrate; 
 forming a first dielectric layer on the metal interconnect layer; 
 forming a second dielectric layer on the first dielectric layer; 
 forming a capacitor metal layer on the second dielectric layer; 
 patterning and etching the capacitor metal layer and the second dielectric layer, the patterning and etching extending into the first dielectric layer to leave a portion of the capacitor metal layer and the second dielectric layer on the first dielectric layer; 
 forming an anti-reflective coating to cover the portion of the capacitor metal layer and the second dielectric layer, and to cover the metal interconnect layer; and 
 patterning the metal interconnect layer to form a first metal layer and a second metal layer, the first metal layer forming a plate of a capacitor. 
 
     
     
       2. The method of  claim 1 , wherein the second dielectric layer has a thickness in a range of 1000 angstroms to 1600 angstroms. 
     
     
       3. The method of  claim 1 , wherein the second dielectric layer comprises silicon nitride and has an index of refraction in a range of 2.3 to 2.9. 
     
     
       4. The method of  claim 1  further comprising:
 forming an inter-layer dielectric, which is in contact with the anti-reflective coating; and 
 patterning and etching the inter-layer dielectric to form a via structure. 
 
     
     
       5. The method of  claim 1 , wherein the capacitor metal layer has a thickness in a range of 1000 angstroms to 1400 angstroms. 
     
     
       6. The method of  claim 1 , wherein the capacitor metal layer comprises titanium nitride. 
     
     
       7. The method of  claim 1 , wherein the first dielectric layer has a thickness in a range of 100 to 200 angstroms. 
     
     
       8. The method of  claim 1 , wherein the anti-reflective coating comprises silicon oxynitride. 
     
     
       9. The method of  claim 8 , wherein the anti-reflective coating has an index of refraction in a range of 1.7 to 2.1. 
     
     
       10. The method of  claim 8 , wherein the anti-reflective coating has a thickness in a range of 100 angstroms to 400 angstroms. 
     
     
       11. A method comprising:
 obtaining a substrate with a metal layer deposited above the substrate; 
 forming a silicon nitride layer on the metal layer; 
 forming a titanium nitride layer on the silicon nitride layer; 
 patterning and etching the titanium nitride layer and the silicon nitride layer to form a capacitor dielectric, leaving a portion of the silicon nitride layer on the metal layer; 
 forming an anti-reflective coating to cover exposed portions of the titanium nitride layer and the silicon nitride layer, exposed portions including sidewalls of the titanium nitride layer and the silicon nitride layer; and 
 patterning the metal layer. 
 
     
     
       12. The method of  claim 11 , wherein the silicon nitride layer has a thickness in a range of 1000 angstroms to 1600 angstroms. 
     
     
       13. The method of  claim 12 , wherein the silicon nitride layer has an index of refraction in a range of 2.3 to 2.9. 
     
     
       14. The method of  claim 12 , wherein the titanium nitride layer has a thickness in a range of 1000 angstroms to 1400 angstroms. 
     
     
       15. The method of  claim 11 , wherein forming the anti-reflective coating comprises forming a silicon oxynitride. 
     
     
       16. The method of  claim 15 , wherein the silicon oxynitride has an index of refraction in a range of 1.7 to 2.1.